The effects of the layer thickness and of Si doping on the dislocation type and density, electron concentration, and deep trap spectra were studied for epitaxially laterally overgrown (ELOG) GaN films with the ELOG region thickness varying from 6 to 12 mu m. Electron beam induced current imaging shows that for the thickest layers, the major part of the threading dislocations are filtered out while for thinner films they bend, but do not go out of play. The concentration of residual donors and major electron traps is found to decrease with increasing the film thickness. Si doping suppresses the concentration of the main electron trap with activation energy of 0.6 eV and enhances the concentration of the main hole trap at E-v+0.85 eV. (C) 2008 American Vacuum Society.